1 use crate::{LateContext, LateLintPass, LintContext};
3 use rustc_errors::{fluent, Applicability};
5 use rustc_infer::infer::TyCtxtInferExt;
6 use rustc_middle::lint::in_external_macro;
8 use rustc_parse_format::{ParseMode, Parser, Piece};
9 use rustc_session::lint::FutureIncompatibilityReason;
10 use rustc_span::edition::Edition;
11 use rustc_span::{hygiene, sym, symbol::kw, InnerSpan, Span, Symbol};
12 use rustc_trait_selection::infer::InferCtxtExt;
15 /// The `non_fmt_panics` lint detects `panic!(..)` invocations where the first
16 /// argument is not a formatting string.
20 /// ```rust,no_run,edition2018
29 /// In Rust 2018 and earlier, `panic!(x)` directly uses `x` as the message.
30 /// That means that `panic!("{}")` panics with the message `"{}"` instead
31 /// of using it as a formatting string, and `panic!(123)` will panic with
32 /// an `i32` as message.
34 /// Rust 2021 always interprets the first argument as format string.
37 "detect single-argument panic!() invocations in which the argument is not a format string",
38 @future_incompatible = FutureIncompatibleInfo {
39 reason: FutureIncompatibilityReason::EditionSemanticsChange(Edition::Edition2021),
40 explain_reason: false,
42 report_in_external_macro
45 declare_lint_pass!(NonPanicFmt => [NON_FMT_PANICS]);
47 impl<'tcx> LateLintPass<'tcx> for NonPanicFmt {
48 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
49 if let hir::ExprKind::Call(f, [arg]) = &expr.kind {
50 if let &ty::FnDef(def_id, _) = cx.typeck_results().expr_ty(f).kind() {
51 let f_diagnostic_name = cx.tcx.get_diagnostic_name(def_id);
53 if Some(def_id) == cx.tcx.lang_items().begin_panic_fn()
54 || Some(def_id) == cx.tcx.lang_items().panic_fn()
55 || f_diagnostic_name == Some(sym::panic_str)
57 if let Some(id) = f.span.ctxt().outer_expn_data().macro_def_id {
59 cx.tcx.get_diagnostic_name(id),
60 Some(sym::core_panic_2015_macro | sym::std_panic_2015_macro)
62 check_panic(cx, f, arg);
65 } else if f_diagnostic_name == Some(sym::unreachable_display) {
66 if let Some(id) = f.span.ctxt().outer_expn_data().macro_def_id {
67 if cx.tcx.is_diagnostic_item(sym::unreachable_2015_macro, id) {
71 // This is safe because we checked above that the callee is indeed
72 // unreachable_display
74 // Get the borrowed arg not the borrow
75 hir::ExprKind::AddrOf(ast::BorrowKind::Ref, _, arg) => arg,
76 _ => bug!("call to unreachable_display without borrow"),
87 fn check_panic<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>, arg: &'tcx hir::Expr<'tcx>) {
88 if let hir::ExprKind::Lit(lit) = &arg.kind {
89 if let ast::LitKind::Str(sym, _) = lit.node {
90 // The argument is a string literal.
91 check_panic_str(cx, f, arg, sym.as_str());
96 // The argument is *not* a string literal.
98 let (span, panic, symbol) = panic_call(cx, f);
100 if in_external_macro(cx.sess(), span) {
101 // Nothing that can be done about it in the current crate.
105 // Find the span of the argument to `panic!()` or `unreachable!`, before expansion in the
106 // case of `panic!(some_macro!())` or `unreachable!(some_macro!())`.
107 // We don't use source_callsite(), because this `panic!(..)` might itself
108 // be expanded from another macro, in which case we want to stop at that
110 let mut arg_span = arg.span;
111 let mut arg_macro = None;
112 while !span.contains(arg_span) {
113 let expn = arg_span.ctxt().outer_expn_data();
117 arg_macro = expn.macro_def_id;
118 arg_span = expn.call_site;
121 cx.struct_span_lint(NON_FMT_PANICS, arg_span, fluent::lint_non_fmt_panic, |lint| {
122 lint.set_arg("name", symbol);
123 lint.note(fluent::note);
124 lint.note(fluent::more_info_note);
125 if !is_arg_inside_call(arg_span, span) {
126 // No clue where this argument is coming from.
129 if arg_macro.map_or(false, |id| cx.tcx.is_diagnostic_item(sym::format_macro, id)) {
130 // A case of `panic!(format!(..))`.
131 lint.note(fluent::supports_fmt_note);
132 if let Some((open, close, _)) = find_delimiters(cx, arg_span) {
133 lint.multipart_suggestion(
134 fluent::supports_fmt_suggestion,
136 (arg_span.until(open.shrink_to_hi()), "".into()),
137 (close.until(arg_span.shrink_to_hi()), "".into()),
139 Applicability::MachineApplicable,
143 let ty = cx.typeck_results().expr_ty(arg);
144 // If this is a &str or String, we can confidently give the `"{}", ` suggestion.
145 let is_str = matches!(
147 ty::Ref(_, r, _) if *r.kind() == ty::Str,
150 Some(ty_def) if Some(ty_def.did()) == cx.tcx.lang_items().string(),
153 let infcx = cx.tcx.infer_ctxt().build();
154 let suggest_display = is_str
157 .get_diagnostic_item(sym::Display)
158 .map(|t| infcx.type_implements_trait(t, [ty], cx.param_env).may_apply())
160 let suggest_debug = !suggest_display
163 .get_diagnostic_item(sym::Debug)
164 .map(|t| infcx.type_implements_trait(t, [ty], cx.param_env).may_apply())
167 let suggest_panic_any = !is_str && panic == sym::std_panic_macro;
169 let fmt_applicability = if suggest_panic_any {
170 // If we can use panic_any, use that as the MachineApplicable suggestion.
171 Applicability::MaybeIncorrect
173 // If we don't suggest panic_any, using a format string is our best bet.
174 Applicability::MachineApplicable
178 lint.span_suggestion_verbose(
179 arg_span.shrink_to_lo(),
180 fluent::display_suggestion,
184 } else if suggest_debug {
185 lint.set_arg("ty", ty);
186 lint.span_suggestion_verbose(
187 arg_span.shrink_to_lo(),
188 fluent::debug_suggestion,
194 if suggest_panic_any {
195 if let Some((open, close, del)) = find_delimiters(cx, span) {
196 lint.set_arg("already_suggested", suggest_display || suggest_debug);
197 lint.multipart_suggestion(
198 fluent::panic_suggestion,
200 vec![(span.until(open), "std::panic::panic_any".into())]
203 (span.until(open.shrink_to_hi()), "std::panic::panic_any(".into()),
207 Applicability::MachineApplicable,
216 fn check_panic_str<'tcx>(
217 cx: &LateContext<'tcx>,
218 f: &'tcx hir::Expr<'tcx>,
219 arg: &'tcx hir::Expr<'tcx>,
222 if !fmt.contains(&['{', '}']) {
223 // No brace, no problem.
227 let (span, _, _) = panic_call(cx, f);
229 if in_external_macro(cx.sess(), span) && in_external_macro(cx.sess(), arg.span) {
230 // Nothing that can be done about it in the current crate.
234 let fmt_span = arg.span.source_callsite();
236 let (snippet, style) = match cx.sess().parse_sess.source_map().span_to_snippet(fmt_span) {
238 // Count the number of `#`s between the `r` and `"`.
239 let style = snippet.strip_prefix('r').and_then(|s| s.find('"'));
240 (Some(snippet), style)
242 Err(_) => (None, None),
245 let mut fmt_parser = Parser::new(fmt, style, snippet.clone(), false, ParseMode::Format);
246 let n_arguments = (&mut fmt_parser).filter(|a| matches!(a, Piece::NextArgument(_))).count();
248 if n_arguments > 0 && fmt_parser.errors.is_empty() {
249 let arg_spans: Vec<_> = match &fmt_parser.arg_places[..] {
250 [] => vec![fmt_span],
253 .map(|span| fmt_span.from_inner(InnerSpan::new(span.start, span.end)))
256 cx.struct_span_lint(NON_FMT_PANICS, arg_spans, fluent::lint_non_fmt_panic_unused, |lint| {
257 lint.set_arg("count", n_arguments);
258 lint.note(fluent::note);
259 if is_arg_inside_call(arg.span, span) {
260 lint.span_suggestion(
261 arg.span.shrink_to_hi(),
262 fluent::add_args_suggestion,
264 Applicability::HasPlaceholders,
266 lint.span_suggestion(
267 arg.span.shrink_to_lo(),
268 fluent::add_fmt_suggestion,
270 Applicability::MachineApplicable,
276 let brace_spans: Option<Vec<_>> =
277 snippet.filter(|s| s.starts_with('"') || s.starts_with("r#")).map(|s| {
279 .filter(|&(_, c)| c == '{' || c == '}')
280 .map(|(i, _)| fmt_span.from_inner(InnerSpan { start: i, end: i + 1 }))
283 let count = brace_spans.as_ref().map(|v| v.len()).unwrap_or(/* any number >1 */ 2);
286 brace_spans.unwrap_or_else(|| vec![span]),
287 fluent::lint_non_fmt_panic_braces,
289 lint.set_arg("count", count);
290 lint.note(fluent::note);
291 if is_arg_inside_call(arg.span, span) {
292 lint.span_suggestion(
293 arg.span.shrink_to_lo(),
296 Applicability::MachineApplicable,
305 /// Given the span of `some_macro!(args);`, gives the span of `(` and `)`,
306 /// and the type of (opening) delimiter used.
307 fn find_delimiters(cx: &LateContext<'_>, span: Span) -> Option<(Span, Span, char)> {
308 let snippet = cx.sess().parse_sess.source_map().span_to_snippet(span).ok()?;
309 let (open, open_ch) = snippet.char_indices().find(|&(_, c)| "([{".contains(c))?;
310 let close = snippet.rfind(|c| ")]}".contains(c))?;
312 span.from_inner(InnerSpan { start: open, end: open + 1 }),
313 span.from_inner(InnerSpan { start: close, end: close + 1 }),
318 fn panic_call<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>) -> (Span, Symbol, Symbol) {
319 let mut expn = f.span.ctxt().outer_expn_data();
321 let mut panic_macro = kw::Empty;
323 // Unwrap more levels of macro expansion, as panic_2015!()
324 // was likely expanded from panic!() and possibly from
325 // [debug_]assert!().
327 let parent = expn.call_site.ctxt().outer_expn_data();
328 let Some(id) = parent.macro_def_id else { break };
329 let Some(name) = cx.tcx.get_diagnostic_name(id) else { break };
332 sym::core_panic_macro
333 | sym::std_panic_macro
335 | sym::debug_assert_macro
336 | sym::unreachable_macro
345 if let hygiene::ExpnKind::Macro(_, symbol) = expn.kind { symbol } else { sym::panic };
346 (expn.call_site, panic_macro, macro_symbol)
349 fn is_arg_inside_call(arg: Span, call: Span) -> bool {
350 // We only add suggestions if the argument we're looking at appears inside the
351 // panic call in the source file, to avoid invalid suggestions when macros are involved.
352 // We specifically check for the spans to not be identical, as that happens sometimes when
353 // proc_macros lie about spans and apply the same span to all the tokens they produce.
354 call.contains(arg) && !call.source_equal(arg)